For instance, a turbocharger for an automobile includes a turbine and a compressor, and a turbine rotor of the turbine and an impeller of the compressor are coupled to each other via a rotor shaft. The rotor shaft is supported rotatably by a radial bearing, which supports loads in the radial direction.
For instance, Patent Document 1 discloses a radial bearing which is a floating bush bearing, and a floating bush bearing includes a floating bush fitted onto a rotor shaft via a gap. The floating bush is disposed in a bearing hole, and an oil path (oil-feed hole) has an opening on an inner peripheral surface of the bearing hole.
The floating bush includes a plurality of lubricant-oil communication holes penetrating through the floating bush diagonally with respect to the radial direction, and lubricant oil supplied in the bearing hole through the oil-feed hole flows inside the floating bush through the lubricant-oil communication holes of the floating bush. The central region of an outer peripheral surface of the floating bush having openings of the lubricant-oil communication holes is formed to have a concave surface, and the concave surface forms a circumferential groove of a constant width over the entire circumference of the outer peripheral surface of the floating bush.